Recording medium recording character area extraction program, information processing apparatus and character area extraction method

ABSTRACT

A non-transitory computer-readable recording medium recording a character area extraction program for causing a computer to execute a process includes changing a relationship in relative sizes between an image and a scanning window that scans the image; scanning the scanning window based on a changed relationship, specifying a scanning position at which an edge density of an image area included in the scanning window is equal to or larger than a threshold value, extracting one or more areas indicated by the scanning window at the specified scanning position as one or more character area candidates, determining, when overlapped character area candidates included in the one or more character area candidates overlap with each other, a maximum character area candidate having a maximum edge density among the overlapped character area candidates, and extracting the image area included in the maximum character area candidate as a character area.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2017-225029, filed on Nov. 22,2017, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a recording medium forrecording a character area extraction program, an information processingapparatus, and a character area extraction method.

BACKGROUND

In a character recognition processing, an area (character area)including characters (e.g., characters written on a signboard or sign)is extracted from, for example, a photographed image captured by animage capturing device. Character recognition is performed with respectto the extracted character area.

Related technologies are disclosed in, for example, Japanese Laid-openPatent Publication No. 2012-108689.

SUMMARY

According to one aspect of the embodiments, a non-transitorycomputer-readable recording medium recording a character area extractionprogram for causing a computer to execute a process includes: changing arelationship in relative sizes between an image and a scanning windowthat scans the image; scanning the scanning window based on a changedrelationship; specifying a scanning position at which an edge density ofan image area included in the scanning window is equal to or larger thana threshold value; extracting one or more areas indicated by thescanning window at the specified scanning position as one or morecharacter area candidates; determining, when overlapped character areacandidates included in the one or more character area candidates overlapwith each other, a maximum character area candidate having a maximumedge density among the overlapped character area candidates; andextracting the image area included in the maximum character areacandidate as a character area.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of an image processing system;

FIG. 2 illustrates an example of a hardware configuration of an imageprocessing apparatus;

FIG. 3 illustrates an example of a functional configuration of acharacter area extracting unit;

FIGS. 4A and 4B illustrate an example of a relationship betweenresolution and edge density;

FIG. 5 illustrates an example of a character area candidate extractionprocessing;

FIG. 6 illustrates an example of an overlapping area extractionprocessing and a character area determination processing;

FIG. 7 illustrates an example of a character area extraction processing;

FIG. 8 illustrates an example of the character area extractionprocessing; and

FIG. 9 illustrates an example of the character area extractionprocessing.

DESCRIPTION OF EMBODIMENTS

In a character recognition processing, it is required that characterareas are extracted from, for example, captured images without excess ordeficiency. However, in the case of characters included in, for example,the captured images, the sizes of characters are not standardized. Forthis reason, a plurality of characters having different sizes isincluded. Therefore, an unextracted character area may occur.

For example, a plurality of images with different resolutions isgenerated. Candidates of the character areas are detected from images ofthe plurality of respective resolutions. An area in which the detectedcharacter area candidates overlap for more than a predetermined numberis extracted as the character area.

According to the extraction method, even in a case where a plurality ofcharacters having different sizes is included, respective characterareas may be extracted.

For example, in the extraction method, the extracted character areaincludes many background images other than characters. For example, anarea wider than an area where characters actually exist is extracted asthe character area. Therefore, an extraction accuracy (a ratio of thearea in which the characters are actually present, which is occupied inthe extracted character area) is low. Therefore, when the characterrecognition is performed using the extracted character area, thecharacter recognition accuracy may decrease.

For example, a technique may be provided, which enhances the extractionaccuracy when extracting the character area from an image.

In the present specification and the drawings, components having asubstantially similar functional configuration will be denoted with thesame reference numeral, and overlapping descriptions thereof will beomitted.

First Embodiment

<System Configuration of Image Processing System>

FIG. 1 illustrates an example of an image processing system.

As illustrated in FIG. 1, the image processing system 100 includes animage providing apparatus 110, an image processing apparatus 120, and aterminal 130. The image providing apparatus 110 is connected to theimage processing apparatus 120 via a wired or wireless network (or theimage providing apparatus 110 is directly set in a drive device of theimage processing apparatus 120). The image processing apparatus 120 andthe terminal 130 are connected to each other via a network 140.

The image providing apparatus 110 is an apparatus or a medium thatprovides image data such as captured images to the image processingapparatus 120, and in the first embodiment, the image providingapparatus 110 includes an imaging apparatus 111 and various recordingmedia 112. The recording medium 112 is a medium capable of storing theimage data, and the recording medium 112 includes a predeterminedmedium.

The image processing apparatus 120 is an example of a character areaextraction apparatus. An image acquisition program and a character areaextraction program are installed in the image processing apparatus 120,and when the program is executed, the image processing apparatus 120serves as an image acquisition unit 121 and a character area extractingunit 122.

The image acquisition unit 121 acquires the image data from the imageproviding apparatus 110 and stores the acquired image data in an imagestorage unit 123. The character area extracting unit 122 reads out theimage data stored in the image storage unit 123 and extracts thecharacter area in each frame included in the image data. The characterarea extracting unit 122 transmits the extracted character area togetherwith the image data to the terminal 130 via the network 140.

The terminal 130 receives the image data transmitted from the characterarea extracting unit 122 via the network 140 and performs a characterrecognition processing with respect to the character area in each frameincluded in the image data. The terminal 130 outputs a result of thecharacter recognition processing.

<Hardware Configuration of Image Processing Apparatus>

FIG. 2 illustrates an example of a hardware configuration of an imageprocessing apparatus. As illustrated in FIG. 2, the image processingapparatus 120 includes a CPU (central processing unit) 201, a read onlymemory (ROM) 202, and a random access memory (RAM) 203. The CPU 201, theROM 202, and the RAM 203 form a so-called computer.

The image processing apparatus 120 includes an auxiliary storage device204, a display device 205, an operation device 206, an interface (I/F)device 207, a communication device 208, and a drive device 209. Further,the respective hardware components of the image processing apparatus 120are connected to each other via a bus 210.

The CPU 201 is an arithmetic device that executes various programs(e.g., image acquisition program and character area extraction program)installed in the auxiliary storage device 204.

The ROM 202 is a nonvolatile memory. The ROM 202 serves as a mainstorage device for storing, for example, various programs and data whichthe CPU 201 requires to execute the various programs installed in theauxiliary storage device 204. For example, the ROM 202 functions as amain storage device for storing, for example, a boot program, such as abasic input/output system (BIOS) or an extensible firmware interface(EFI).

The RAM 203 is a volatile memory such as a dynamic random access memory(DRAM) or a static random access memory (SRAM). The RAM 203 serves as amain storage device for providing a working area developed when variousprograms installed in the auxiliary storage device 204 are executed bythe CPU 201.

The auxiliary storage device 204 is an auxiliary storage device thatstores, for example, various programs and image data processed byexecution of various programs. For example, the image storage unit 123is implemented by the auxiliary storage device 204.

The display device 205 is a display device for displaying, for example,an internal state of the image processing apparatus 120. The operationdevice 206 is an input device for an administrator of the imageprocessing apparatus 120 to input various instructions to the imageprocessing apparatus 120.

The I/F device 207 is a connection device for connecting with, forexample, the imaging apparatus 111 in the image providing apparatus 110.The communication device 208 is a communication device for communicatingwith the terminal 130 via the network 140.

The drive device 209 is a device for setting, for example, the recordingmedium 112 in the image providing apparatus 110. The recording medium112 referred to here includes, for example, a medium that optically,electrically, or magnetically records information, such as a CD-ROM, aflexible disk or a magneto-optical disk. The recording medium 112 mayinclude, for example, a semiconductor memory for electrically recordinginformation, such as, for example, a ROM, or a flash memory.

The drive device 209 may be used when installing various programs in theauxiliary storage device 204. For example, an administrator of the imageprocessing apparatus 120 sets the distributed recording medium 112 inthe drive device 209 to allow the driver device 209 to read out variousprograms recorded in the recording medium 112, so that various kinds ofprograms may be installed in the auxiliary storage device 204.

Alternatively, installation of various programs in the auxiliary storagedevice 204 may be performed via the communication device 208. Forexample, the administrator of the image processing apparatus 120 maydownload various programs from the network 140 via the communicationdevice 208, so that various programs may be installed in the auxiliarystorage device 204.

<Functional Configuration of Character Area Extracting Unit>

FIG. 3 illustrates an example of a functional configuration of acharacter area extracting unit.

As illustrated in FIG. 3, the character area extracting unit 122includes an image read-out unit 301, a relative size changing unit 302,a scanning unit 303, a character area candidate extracting unit 304, anoverlapping area extracting unit 305, a character area determining unit306, and an output unit 307.

The image read-out unit 301 reads out the image data stored in the imagestorage unit 123 for each frame and notifies the read-out image data tothe relative size changing unit 302.

The relative size changing unit 302 is an example of a changing meansand changes the resolution with respect to the notified image datahaving a unit of frame. The relative size changing unit 302 sequentiallychanges the resolution on the basis of a predetermined change pattern tosequentially change the relationship of a relative size between theimage data and a scanning window having a fixed size.

For example, the relative size changing unit 302 sequentially changesthe vertical resolution in a state where the horizontal resolution ofthe image data is fixed to a predetermined resolution. When the changeof the vertical resolution is completed for a predetermined changerange, the relative size changing unit 302 continuously fixes thehorizontal resolution of the image data to another resolution andsimilarly changes the vertical resolution in sequence. The relative sizechanging unit 302 repeats the processing and achieves a combination ofall of the vertical and horizontal resolutions by completing a change ofa predetermined change range with respect to the horizontal resolution.

Every time the resolution of the image data is changed based on thepredetermined change pattern, the scanning unit 303 scans the image dataof the resolution after the change by using the fixed size scanningwindow. The scanning unit 303 extracts an image area included in thescanning window at each scanning position and notifies the extractedimage area to the character area candidate extracting unit 304.

The character area candidate extracting unit 304 is an example of anextraction means and extracts edge pixels from the image area includedin the scanning window and calculates the edge density of the imagearea. The edge density refers to a ratio of the number of pixels of theedge pixel to the total number of pixels of the image area included inthe scanning window.

The character area candidate extracting unit 304 specifies a scanningposition at which the calculated edge density is equal to or larger thana predetermined threshold value and extracts an area indicated by thescanning window at a specified scanning position as a character areacandidate. Furthermore, the character area candidate extracting unit 304notifies the extracted character area candidate to the overlapping areaextracting unit 305 together with the (vertical and horizontal)resolution at that time.

The overlapping area extracting unit 305 enlarges or reduces thecharacter area candidate notified from the character area candidateextracting unit 304. For example, the overlapping area extracting unit305 calculates an enlargement ratio or a reduction ratio when enlargingor reducing the image data from which each character area candidate isextracted to image data of unified resolution, and enlarges or reducesthe character area candidate.

The overlapping area extracting unit 305 arranges the enlarged orreduced character area candidates in the image data of unifiedresolution. Further, the overlapping area extracting unit 305 determineswhether the character area candidates overlap with each other in apredetermined threshold area or more with respect to the image data inwhich the enlarged or reduced character area candidate is arranged. Whenit is determined that the character area candidates overlap with eachother in the predetermined threshold area or more, the overlapping areaextracting unit 305 extracts overlapping character area candidates andassociates the extracted character area candidates with each other.

The character area determining unit 306 is an example of a determinationunit, and determines a character area candidate having maximum edgedensity from the character area candidates associated by the overlappingarea extracting unit 305. The character area determining unit 306extracts the image area included in the determined character areacandidate as the character area.

The output unit 307 outputs the character area extracted by thecharacter area determining unit 306 in association with the image dataof a processing target frame.

<Relationship of Resolution and Edge Density>

The relationship between the image data with the changed resolution andthe edge density of the image area included in the scanning window ateach scanning position in the image data of each resolution will bedescribed. FIGS. 4A and 4B illustrate an example of a relationshipbetween resolution and edge density.

FIG. 4A illustrates each image data when vertical resolution issequentially changed in a state where horizontal resolution of imagedata is fixed to predetermined resolution and edge density of an imagearea included in a scanning window at a predetermined scanning positionin the image data of each resolution.

Each image data illustrated in FIG. 4A is displayed by fixing the sizeof the pixel. Therefore, in each image data illustrated in FIG. 4A, thevertical size is displayed larger as the vertical resolution becomeshigher.

As illustrated in FIG. 4A, in the case of image data 402 having a highervertical resolution than that of image data 401, the edge density of theimage area included in the fixed-size scanning window 400 is higher thanthat in the case of the image data 401. Similarly, in the case of imagedata 403 having higher vertical resolution than the image data 402, theedge density of the image area included in the fixed-size scanningwindow 400 is higher than that in the case of the image data 402.Similarly, in the case of image data 404 having higher verticalresolution than the image data 403, the edge density of the image areaincluded in the fixed-size scanning window 400 is higher than that inthe case of the image data 403. Meanwhile, in the case of image data 405having higher vertical resolution than the image data 404, the edgedensity of the image area included in the fixed-size scanning window 400is lower than in the case of the image data 404.

As described above, the edge density of the image area included in thefixed-size scanning window 400 is maximized in a state in which thecharacters in the image area are vertically inscribed in the fixed-sizescanning window 400.

FIG. 4B illustrates each image data in a case where the horizontalresolution is sequentially changed in a state where vertical resolutionof image data is fixed to predetermined resolution, and an edge densityof an image area included in a scanning window at a predeterminedscanning position in the image data of each resolution.

Similarly to FIG. 4A, each image data illustrated in FIG. 4B is alsodisplayed by fixing the size of the pixel. Therefore, in each image dataillustrated in FIG. 4B, the horizontal size is displayed larger as thehorizontal resolution becomes higher.

As illustrated in FIG. 4B, in the case of image data 412 having higherhorizontal resolution than image data 411, the edge density of the imagearea included in the fixed-size scanning window 400 is higher than inthe case of the image data 411. Similarly, in the case of image data 413having higher horizontal resolution than the image data 412, the edgedensity of the image area included in the fixed-size scanning window 400is higher than in the case of the image data 412. Similarly, in the caseof image data 414 having higher horizontal resolution than the imagedata 413, the edge density of the image area included in the fixed-sizescanning window 400 is higher than in the case of the image data 413.Meanwhile, in the case of image data 415 having a higher horizontalresolution than that of the image data 414, the edge density of theimage area included in the fixed-size scanning window 400 is lower thanin the case of the image data 414.

As described above, the edge density of the image area included in thefixed-size scanning window 400 is maximized in a state in which thecharacters in the image area are horizontally inscribed in thefixed-size scanning window 400.

Therefore, by sequentially changing the vertical and horizontalresolution of the image data and determining the resolution at which theedge density becomes the maximum, it is possible to extract an imagearea in which the characters are inscribed in the scanning window in thevertical direction and the horizontal direction. That is, it is possibleto extract character areas with high extraction accuracy, in whichbackground images other than the characters are excluded as much aspossible.

<Overview of Character Area Candidate Extraction Processing>

The character area candidate extracting unit 304 performs the characterarea candidate extraction processing. FIG. 5 illustrates an example ofthe character area candidate extraction processing. As described above,the relative size changing unit 302 generates image data of an arbitrarycombination of all resolutions within a predetermined change range inthe vertical direction and all resolutions within a predetermined changerange in the horizontal direction. However, in FIG. 5, for simplicity ofdescription, only a combination of some of the resolutions is excerptedand represented. The scanning unit 303 performs scanning using thescanning window 400 with respect to all of the areas in the image datawhose resolution is changed, but here, the scanning unit 303 will bedescribed by considering a scanning position at which a predeterminedcharacter “523” is drawn in the image data.

When the position at which the predetermined character “523” in theimage data is drawn becomes the scanning position, the edge densitycalculated by the character area candidate extracting unit 304 ischanged with the change of the vertical resolution of the image data asillustrated in (a) of FIG. 5.

Among them, image data 403 to 405 in which the edge density is equal toor larger than a predetermined threshold value Th1 are considered. Withrespect to the vertical resolutions of the respective image data 403 to405, when five image data having different horizontal resolutions fromeach other are excerpted to make the edge density into a graph, the edgedensity is illustrated in (b-1) to (b-3) of FIG. 5.

As illustrated in respective (b-1) to (b-3) of FIG. 5, image data (e.g.,image data 521 to 542) other than the image data 403 to 405 among fiveimage data having different horizontal resolutions have higher edgedensity than the image data 403 to 405.

The character area candidate extracting unit 304 specifies image data521, 531, and 541 having a resolution in which the edge density is equalto or larger than a predetermined threshold value Th2 among the imagedata. The character area candidate extracting unit 304 extracts the areaindicated by the scanning window 400 for the specified image data 521,531, and 541 as character area candidates 551, 552, and 553.

<Overview of Overlapping Area Extraction Processing and Character AreaDetermination Processing>

The overlapping area extracting unit 305 performs the overlapping areaextraction processing, and the character area determining unit 306performs the character area determination processing. FIG. 6 illustratesan example of the overlapping area extraction processing and thecharacter area determination processing.

As illustrated in FIG. 6, the overlapping area extracting unit 305enlarges or reduces the sizes of the character area candidates 551, 552,and 553 extracted from the image data 521, 531, and 541.

For example, the overlapping area extracting unit 305 calculates theenlargement ratio or the reduction ratio when enlarging or reducing theimage data 521, 531, and 541 to image data 521′, 531′, and 541′ ofunified resolution. For example, the overlapping area extracting unit305 calculates the enlargement ratio when enlarging the image data 521to the image data 521′, and enlarges the character area candidate 551using the enlargement ratio to obtain a character area candidate 551′.The overlapping area extracting unit 305 calculates the enlargementratio when enlarging the image data 531 to the image data 531′, andenlarges the character area candidate 552 using the enlargement ratio toobtain a character area candidate 552′. Further, the overlapping areaextracting unit 305 calculates the reduction ratio when reducing theimage data 541 to the image data 541′ and reduces the character areacandidate 553 using the reduction ratio to obtain a character areacandidate 553′.

Subsequently, the overlapping area extracting unit 305 arranges theenlarged or reduced character area candidates 551′, 552′, and 553′ inthe unified resolution image data (here, the image data 531′) todetermine whether overlapping occurs.

In the case of the example of FIG. 6, since the character areacandidates 551′, 552′, and 553′ overlap with each other in apredetermined threshold area or more, the overlapping area extractingunit 305 determines that the character area candidates 551′, 552′, and553′ overlap with each other and extracts the character area candidates.The overlapping area extracting unit 305 associates the extractedcharacter area candidates with each other.

The character area determining unit 306 determines a character areacandidate having maximum edge density among the character areacandidates 551′, 552′, and 553′ associated by the overlapping areaextracting unit 305. The example of FIG. 6 indicates that it isdetermined that the edge density of the image area included in thecharacter area candidate 552′ among the character area candidates 551′,552′, and 553′ becomes the maximum.

<Flow of Character Area Extraction Processing>

The character area extracting unit 122 performs a character areaextraction processing. FIGS. 7 to 9 illustrate an example of thecharacter area extraction processing.

In step S701, the image read-out unit 301 reads out image data 900 (FIG.9) of the processing target frame from the image storage unit 123. Instep S702, the scanning unit 303 reads out the fixed-size scanningwindow 400.

In step S703, the relative size changing unit 302 initializes thevertical resolution and the horizontal resolution to predeterminedresolution with respect to the read-out image data 900.

In step S704, the relative size changing unit 302 changes the verticalresolution in a state where the horizontal resolution is fixed withrespect to the image data whose resolution is initialized.

In step S705, the scanning unit 303 scans the image data whose verticalresolution is changed in step S703 using the fixed-size scanning window400.

In step S706, the character area candidate extracting unit 304 performsan edge processing on the image area at each scanning position of thescanning window 400 performing scanning to detect edge pixels. Thecharacter area candidate extracting unit 304 calculates the edge densityof the image area at each scanning position based on the detected edgepixels, thereby specifying the scanning position having the edge densityequal to or larger than the predetermined threshold value Th2.Furthermore, the character area candidate extracting unit 304 extractsthe area indicated by the scanning window at the specified scanningposition as the character area candidate.

In step S707, the character area candidate extracting unit 304associates and maintains the extracted character area candidate with theedge density and the (vertical and horizontal) resolutions.

In step S708, the relative size changing unit 302 determines whether allvertical resolutions in a predetermined change range have been covered.When it is determined in step S708 that all the vertical resolutionshave not been covered (in the case of “No” in step S708), the processreturns to step S704. Meanwhile, when it is determined in step S708 thatall the vertical resolutions in the predetermined change range have beencovered (in the case of “Yes” in step S708), the process proceeds tostep S709.

In step S709, the relative size changing unit 302 determines whether toall horizontal resolutions in the predetermined change range have beencovered. When it is determined in step S709 that all the horizontalresolution have not been covered (in the case of “No” in step S709), theprocess proceeds to step S710.

In step S710, the relative size changing unit 302 initializes thevertical resolution to the predetermined resolution. In step S711, therelative size changing unit 302 changes the horizontal resolution, andthe process proceeds to step S704.

As a result, in a state in which the horizontal resolution is fixed tothe horizontal resolution newly changed in step S711, the scanningwindow 400 is scanned while sequentially changing the verticalresolution in steps S704 to S708 to extract the character areacandidates.

In FIG. 9, image data 910 represents image data in a predeterminedvertical resolution when scanning the scanning window 400 while changingthe vertical resolution in step S704 in a state the newly changedhorizontal resolution is fixed in step S711. In the case of the imagedata 910, the scanning window 400 is scanned to extract character areacandidates 911 and 912.

Image data 920 represents image data in a predetermined verticalresolution when scanning the scanning window 400 while changing thevertical resolution in step S704 in a state in which a further changedhorizontal resolution is fixed in step S711. In the case of the imagedata 920, the scanning window 400 is scanned to extract character areacandidates 921, 922, and 923.

Image data 930 represents image data in a predetermined verticalresolution when scanning the scanning window 400 while changing thevertical resolution in step S704 in a state a further changed horizontalresolution is fixed in step S711. In the case of the image data 930, thescanning window 400 is scanned to extract character area candidates 931and 932.

FIG. 7 will be referred back. When it is determined in step S709 thatall the horizontal resolutions in the predetermined change range havebeen covered (in the case of “Yes” in step S709), the process proceedsto step S801 of FIG. 8.

In step S801, the overlapping area extracting unit 305 reads out thecharacter area candidates 911, 912, 922, 923, 931, and 932 held in stepS707. The overlapping area extracting unit 305 calculates an enlargementratio or a reduction ratio for rendering the resolution (verticaldirection, horizontal direction) associated with the read-out characterarea candidate to a unified resolution. Further, based on the calculatedenlargement ratio or reduction ratio, the overlapping area extractingunit 305 enlarges or reduces the character area candidates 911 to 932and arranges the character area candidates 911 to 932 in the image dataof the unified resolution.

In FIG. 9, image data 940 represents the image data of the unifiedresolution. Character area candidates 911′ to 932′ represent states inwhich the character area candidates 911 to 932 held in step S707 areenlarged or reduced and arranged in the image data 940, respectively.

For example, the character area candidate 911′ represents a state of thecharacter area candidate 911 extracted from the image data 910, which isenlarged based on the enlargement ratio of the image data 910 for theimage data 940 and arranged in the image data 940. The character areacandidate 912′ represents a state of the character area candidate 912extracted from the image data 910, which is enlarged based on theenlargement ratio of the image data 910 for the image data 940 andarranged in the image data 940.

Similarly, the character area candidate 921′ represents a state of thecharacter area candidate 921 extracted from the image data 920 which isenlarged based on the enlargement ratio of the image data 920 for theimage data 940 and arranged in the image data 940. The character areacandidate 922′ represents a state of the character area candidate 922extracted from the image data 920, which is enlarged based on theenlargement ratio of the image data 920 for the image data 940 andarranged in the image data 940. The character area candidate 923′represents a state of the character area candidate 923 extracted fromthe image data 920, which is enlarged based on the enlargement ratio ofthe image data 920 for the image data 940 and arranged in the image data940.

Similarly, the character area candidate 931′ represents a state of thecharacter area candidate 931 extracted from the image data 930 which isenlarged based on the enlargement ratio of the image data 930 for theimage data 940 and arranged in the image data 940. The character areacandidate 932′ represents a state of the character area candidate 932extracted from the image data 930, which is enlarged based on theenlargement ratio of the image data 930 for the image data 940 andarranged in the image data 940.

FIG. 8 will be referred back. In step S802, the overlapping areaextracting unit 305 determines whether the character area candidatesarranged in the image data of the unified resolution overlap with eachother in a predetermined threshold area or more. When it is determinedthat the character area candidates overlap with each other in thepredetermined threshold area or more, the overlapping area extractingunit 305 extracts overlapping character area candidates and associatesthe extracted character area candidates with each other.

Image data 950 of FIG. 9 indicates that it is determined that thecharacter area candidates 912′, 923′, 931′, and 932′ among the characterarea candidates 911′ to 932′ arranged in the image data 940 of theunified resolution overlap with each other and associated with eachother.

In step S803, the character area determining unit 306 determines acharacter area candidate having the maximum edge density among characterarea candidates associated with each other. Image data 960 of FIG. 9indicates that it is determined that the edge density of the characterarea candidate 912′ is the maximum among the edge densities of thecharacter area candidates 912′, 923′, 931′, and 932′ associated witheach other.

In step S804, the character area determining unit 306 extracts the imagearea included in the character area candidate 912′ determined to havethe maximum edge density as the character area.

As is apparent from the above description, the character area extractingdevice according to the first embodiment scans the image data of theframe to be processed while changing the resolution by using the fixedscanning window to specify each scanning position at which the edgedensity is equal to or larger than a predetermined threshold value. Thecharacter area extracting device according to the first embodimentextracts the area indicated by the scanning window as the character areacandidate at each specific scanning position. The character areaextracting device according to the first embodiment arranges theextracted character area candidates in the image data of the unifiedresolution and determines the character area candidate having themaximum edge density among the character area candidates which overlapwith each other. Furthermore, the character area extracting deviceaccording to the first embodiment extracts the image area included inthe determined character area candidate as the character area.

As described above, by extracting the character area based on the edgedensity, it is possible to extract the image area in which thecharacters are inscribed in the scanning window as the character area.That is, it is possible to extract character areas with high extractionaccuracy, in which background images other than the characters areexcluded as much as possible.

Second Embodiment

In the first embodiment, the relative size changing unit 302 has beendescribed as sequentially changing the vertical resolution with thehorizontal resolution fixed first, however, a changing order is notlimited thereto. For example, the horizontal resolution may besequentially changed while the vertical resolution is first fixed.

In the first embodiment, the character recognition processing isdescribed as being executed in the terminal 130, but the characterrecognition processing may be executed by the image processing apparatus120. In the first embodiment, it is described that the character areaextraction processing is performed by the character area extracting unit122 of the image processing apparatus 120, but a part of the function ofthe character area extracting unit 122 may be installed in anotherdevice and executed by a plurality of apparatuses (e.g., by the system).The plurality of corresponding apparatuses may include the imagingapparatus 111 or the terminal 130.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to an illustrating of thesuperiority and inferiority of the invention. Although the embodimentsof the present invention have been described in detail, it should beunderstood that the various changes, substitutions, and alterationscould be made hereto without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A non-transitory computer-readable recordingmedium recording a character area extraction program for causing acomputer to execute a process comprising: changing a relationship inrelative sizes between an image and a scanning window that scans theimage; scanning the scanning window based on a changed relationship;specifying a scanning position at which an edge density of an image areaincluded in the scanning window is equal to or larger than a thresholdvalue; extracting one or more areas indicated by the scanning window atthe specified scanning position as one or more character areacandidates; determining, when overlapped character area candidatesincluded in the one or more character area candidates overlap with eachother, a maximum character area candidate having a maximum edge densityamong the overlapped character area candidates; and extracting the imagearea included in the maximum character area candidate as a characterarea.
 2. The non-transitory computer-readable recording medium accordingto claim 1, wherein a size of the scanning window is fixed, a horizontalresolution of the image is fixed, and a vertical resolution of the imageis sequentially changed, to change the relationship in the relativesizes between the image and the scanning window for scanning the image.3. The non-transitory computer-readable recording medium according toclaim 1, wherein the size of the scanning window is fixed, the verticalresolution of the image is fixed, and the horizontal resolution of theimage is sequentially changed to change the relationship in the relativesizes between the image and the scanning window for scanning the image.4. The non-transitory computer-readable recording medium according toclaim 1, further comprising: enlarging or reducing the size of the oneor more character area candidates by using an enlargement ratio or areduction ratio when changing the relationship in the relative size to apredetermined relationship; and extracting the overlapped character areacandidates which overlap with each other from among enlarged or reducedcharacter area candidates.
 5. An information processing apparatuscomprising: a memory; and a processor coupled to the memory andconfigured to preform operations of: changing a relationship in relativesizes between an image and a scanning window that scans the image;scanning the scanning window based on a changed relationship; specifyinga scanning position at which an edge density of an image area includedin the scanning window is equal to or larger than a threshold value;extracting one or more areas indicated by the scanning window at thespecified scanning position as one or more character area candidates;determining, when overlapped character area candidates included in theone or more character area candidates overlap with each other, a maximumcharacter area candidate having a maximum edge density among theoverlapped character area candidates; and extracting the image areaincluded in the maximum character area candidate as a character area. 6.The information processing apparatus according to claim 5, wherein asize of the scanning window is fixed, a horizontal resolution of theimage is fixed, and a vertical resolution of the image is sequentiallychanged, to change the relationship in the relative sizes between theimage and the scanning window for scanning the image.
 7. The informationprocessing apparatus according to claim 5 wherein the size of thescanning window is fixed, the vertical resolution of the image is fixed,and the horizontal resolution of the image is sequentially changed tochange the relationship in the relative sizes between the image and thescanning window for scanning the image.
 8. The information processingapparatus according to claim 5, wherein the operations include:enlarging or reducing the size of the one or more character areacandidates by using an enlargement ratio or a reduction ratio whenchanging the relationship in the relative size to a predeterminedrelationship; and extracting the overlapped character area candidateswhich overlap with each other from among enlarged or reduced characterarea candidates.
 9. A character area extraction method comprising:changing, by a computer, a relationship in relative sizes between animage and a scanning window that scans the image; scanning the scanningwindow based on a changed relationship; specifying a scanning positionat which an edge density of an image area included in the scanningwindow is equal to or larger than a threshold value; extracting one ormore areas indicated by the scanning window at the specified scanningposition as one or more character area candidates; determining, whenoverlapped character area candidates included in the one or morecharacter area candidates overlap with each other, a maximum characterarea candidate having a maximum edge density among the overlappedcharacter area candidates; and extracting the image area included in themaximum character area candidate as a character area.
 10. The characterarea extraction method according to claim 9, wherein a size of thescanning window is fixed, a horizontal resolution of the image is fixed,and a vertical resolution of the image is sequentially changed, tochange the relationship in the relative sizes between the image and thescanning window for scanning the image.
 11. The character areaextraction method according to claim 9, wherein the size of the scanningwindow is fixed, the vertical resolution of the image is fixed, and thehorizontal resolution of the image is sequentially changed to change therelationship in the relative sizes between the image and the scanningwindow for scanning the image.
 12. The character area extraction methodaccording to claim 9 further comprising: enlarging or reducing the sizeof the one or more character area candidates by using an enlargementratio or a reduction ratio when changing the relationship in therelative size to a predetermined relationship; and extracting theoverlapped character area candidates which overlap with each other fromamong enlarged or reduced character area candidates.